Airbag systems are widely used in the automobile industry and have provided vehicle occupants with enhanced safety for many years. In an automotive vehicle, it is common to position airbags in the hub of the steering wheel, in a recess in the dashboard, in the seats, in the door panels and/or in the body pillars (e.g., the A-pillar, the B-pillar, and C-pillar). Other positions are of course also possible. In any mounting positions, the airbag is required to inflate quickly, at a correct point in time, and at a predictable rate of inflation. For the purpose of simplicity and brevity, inflatable restraints are defined herein to include airbags, curtain bags and the like and a curtain bag is defined herein as a type of airbag.
An airbag of a vehicle is typically in fluid communication with a gas emitting inflator, which in turn is typically in electrical communication with one or more impact sensors. During an impact between the vehicle and another object (e.g., another vehicle, a roadside obstacle, pedestrians, etc.), one or more of the impact sensors (e.g., an accelerometer) detects rapid deceleration of the vehicle in response to the vehicle colliding with the other object. This collision generates an impact pulse that propagates through the vehicle and causes occupants of the vehicle to exhibit relative movement in a direction generally opposite a direction of the impact (e.g., a collision at a particular side of the vehicle will cause relative movement of the occupants toward that particular side of the vehicle). Upon detection of the impact from the collision, the one or more impact sensors will trigger the gas emitting inflator to inflate one or more airbags (i.e., deploy the airbag(s)), which restrains and cushions a vehicle occupant whose movement brings him/her into contact with the deployed airbag. The relative velocities of the vehicle and object involved in the collision will determine whether relative movement of the vehicle occupants is due to inertia of the occupants from movement of the vehicle prior to the collision (e.g., the vehicle is moving and hits a fixed object) and/or from movement of the vehicle initiated by being hit by a moving object (e.g., the vehicle is stationary and is hit by a moving object).
It is known that sensing technologies such as, for example, RADAR (Radio Detection and Ranging), LIDAR (Light Detection and Ranging) and visual imaging can be used in a vehicle for implementing pre-crash sensing of a collision to improve occupant safety. Pre-crash refers to sensing conditions that indicate that a collision between a vehicle and another object is imminent or highly probable. Pre-crash sensing technology has been recognized to have the potential of improving occupant safety by deploying passive restraints devices earlier in a crash, or even before the actual impact. This extra time allows more flexibility for component design and can allow the passive restraints system to be individually tailored to the occupant and crash scenario.
Side impact collisions are a common type of collision for a vehicle. Generally, side impact collisions have a high potential for injuries to vehicle occupants due to the close proximity of the occupants to side structures of the vehicle (e.g., doors, pillars, etc.). To enhance occupant protection in side impact collisions, automobile manufacturers provide adequate side structural stiffness and employ side airbag protection systems. However, due to the close proximity of the occupants of such side structures (e.g., physically closer to an adjacent door than to the steering wheel or dashboard), a side airbag of a side airbag protection system will typically have only a few milliseconds for full deployment before the side structure intrudes into the vehicle occupant compartment and/or an adjacent vehicle occupant moves a substantial distance toward such side structure. Accordingly, the ability of pre-crash sensing to allow for airbag deployment earlier in a collision or even before the actual collision occurs is especially beneficial in side impact collisions.
One approach to benefiting from such improvement in sensing time resulting from pre-crash sensing is an earlier deployment time and the ability to increase a thickness of an airbag that is deployable via pre-crash sensing. The increase in lateral thickness of an airbag increases the cushioning available from the airbag (i.e., the airbag is an inflatable cushion) to an occupant thereby enhancing injury protection afforded by the airbag. However, a typical side airbag protection system employs a single-stage gas emitting inflator (e.g., emits a given amount of gas regardless of specific collision conditions) and an airbag with fixed lateral thickness (i.e., a given volume of bag for a given amount of inflation gas). Because inflation varies as a function of time, an airbag configured for use in a vehicle equipped with pre-crash sensing technologies cannot necessarily be used in a vehicle equipped without pre-crash sensing technologies. This is because of the increased duration of time to implement deployment of an airbag with pre-crash sensing leads to benefits realized through an airbag with greater volume (e.g., increased lateral thickness). As such, if this same large volume airbag were used in a vehicle without pre-crash sensing, an insufficient amount of time would be provided from actual crash detection for allowing a specified degree of inflation of the airbag (i.e., assuming a similar or common volumetric rate of inflation is used with both sensing technologies).
Therefore, an airbag assembly configured to benefit from advanced crash sensing time associated with pre-crash sensing technology and configured in a manner allowing it to be used both in a vehicle with pre-crash sensing technology and in a vehicle without pre-crash sensing technology without modification or reconfiguration would be advantageous, desirable and useful. Also, due to the predict nature of pre-crash sensing using radar, vision, lidar or ultra-sonic sensing systems, in some rare situations, the pre-crash sensing system may not detect a collision situation. Therefore, it is advantageous to use an airbag assembly configured to function effectively in a vehicle equipped with pre-crash sensing system when the pre-crash sensing system does or does not detect a collision situation.